This invention relates generally to a baler for forming cylindrical bales of crop material, commonly referred to as a round baler. More particularly, this invention is directed to twine wrapping apparatus for such round balers.
Balers of this type comprise a bale forming chamber defined by an array of belts, chains, and/or rolls in which the cylindrical bale is formed. Crop material such as hay is picked up from the ground as the baler traverses the field and is then fed into the chamber to be rolled up to form a cylindrical bale. Wrapping apparatus is provided for binding the bale inside the bale forming chamber before being discharged onto the ground for subsequent handling. It is common to utilize twine tubes to feed one or two strands of twine to the circumference of the formed bale during the process of helically wrapping the twine around the bale. The twine tubes are moved such that the strand feeding point varies along a transverse path adjacent the outer surface of the bale as the bale is turned in the chamber.
As noted above, to accomplish such wrapping the formed cylindrical bale is rotated in the bale forming chamber by the crop roll forming apparatus. During this operation additional crop material is not being introduced into the chamber, and accordingly, the baler is unable to function in its principle manner, i.e., it is not traveling across the field, picking up crop material and feeding it into the chamber to roll it into a cylindrical package. Prior art round balers have been designed to minimize this non-crop-feeding phase of the baling operation. For example, efforts have been made to reduce the wrapping time and thereby increase overall productivity by increasing the field travel time relative to the wrapping time. One approach involves the use of dual twine feeding devices such as those shown for exemplary purposes in U.S. Pat. No. 4,517,890, U.S. Pat. No. 4,557,189 and U.S. Pat. No. 4,800,811. These devices feed twine at approximately twice the rate of a single twine arm arrangement, resulting in a more favorable ratio of field working time versus twine wrapping time.
There have been various approaches to improve other aspects of the twine wrapping operation of round balers. For example, it is important that the initial free end of the strand, commonly referred to as the "tail", is positioned as close to the outer surface of the bale as possible to assure that the twine is immediately and properly fed to the circumference of the bale being wrapped. In many prior art arrangements directed to solving these problems, as in the case of the dual arm concept, the wrapping apparatus is typically mounted in the vicinity of the crop infeed area where significant amounts of dust and debris are common, especially during dry field conditions. There are detrimental effects caused by such dust and debris which increases the closer the apparatus is mounted to the baling chamber where the crop material is being agitated by the roll forming mechanism. A major problem with such closely positioned prior art arrangements is that debris tends to accumulate on the twine feeding elements and interferes with their smooth operation and thus affects the overall reliability of the baler. Also, this accumulation of debris can reach levels where it disrupts crop infeed during the following bale formation.
Another concern is that the abrasive characteristics of this dust and debris can and in fact does cause serious wear problems when it comes in contact with the wrapping apparatus which comprises various intermeshing and moving mechanisms arranged to effectively position and guide the twine across the baling chamber infeed area. These wear problems in turn have an unfavorable effect on the overall durability and reliability of the baler.